1. Field of the Invention
The present invention relates to a magnetic tape recording signal level automatic adjustment device for automatically adjusting the level of reproduced audio analog signals from a PCM audio signal reproduction device such as a compact disk player to thereby optimize the recording of reproduced audio signals.
2. Related Art
If reproduced music signals from a compact disk are recorded on a magnetic tape at an ordinary recording sensitivity, there arise some problems: the recorded music signals are subject to distortion because of a high reproduced signal level at a compact disk player, and conversely because of a low reproduced signal level the recorded music signals have a poor S/N ratio. Such problems result from the following reasons:
(1) The dynamic range of a compact disk is wider than that of a magnetic tape by about 40 dB.
(2) There are large differences between the recording levels of different labels of compact disks: the difference between the maximum peak levels may sometimes be as high as 18 dB. Even in the same level, some music program has a maximum peak level of only -13 dB.
To solve such problems, a tape recorder having a conventional automatic level control (ALC) circuit has been used, or the recording level of a tape deck is adjusted to an optimum level prior to recording.
An ALC circuit, however, has been found not satisfactory in that, if a signal indicated by a solid line shown in FIG. 14 is inputted to the ALC circuit, it is attenuated or compressed as shown by the dotted line when it exceeds a certain level so that the original signals are recorded with a low dynamic range and a poor fidelity.
In addition, if an input signal to the ALC circuit has a long attack time, a distortion occurs. In case of a short recovery time, the bleeding phenomenon occurs.
Alternatively, if a manual recording level adjustment method is used, it becomes necessary to adjust the recording level, prior to actual recording, by setting a compact disk player at play and a tape recorder at pause and thereafter, the compact disk player and the tape recorder are stopped to prepare an actual recording.
Such adjustment must be made for all music programs to be recorded due to the above reason (2). Thus, the adjustment becomes quite cumbersome and takes a long time.